Doing exercises, this question came to my mind.
Is it true that if $I$ and $J$ are proper and nonzero ideals of a ring $R$, $$IJ=I \implies I=J?$$
And $$IJ=I \iff I\subseteq J?$$
Doing exercises, this question came to my mind.
Is it true that if $I$ and $J$ are proper and nonzero ideals of a ring $R$, $$IJ=I \implies I=J?$$
And $$IJ=I \iff I\subseteq J?$$
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Automatically if $I=IJ$ then $I=IJ\subseteq J$ i.e. $I\subseteq J$. But equality isn't necessarily true.
Consider $R=F\times F\times F$ and the ideals $I$ and $J$ generated by $(1,0,0)$ and $(1,1,0)$.
Moreover, equality can occur when $I=I^2$ but can't occur if $I\ne I^2$.